Does anyone know the boiling point of solder (yes boiling)

[Psi]

Does anyone know the boiling point of solder (yes boiling)? A quick google attempt let me down.

It's more just a curiosity at the moment.
If i used the TIG torch to heat some metal flat bar to brazing temp ~1000C and fed in some non-fluxed solder wire, would the solder boil and explode? etc.

[bson]

For leaded, same as lead, about 1700˚C.  For lead free, probably a bit higher.

I.e., a bit above the melting point of iron, so it's seems unlikely you'd make it boil.  However, impurities like water or oil or something might vaporize explosively at much lower temperatures...

[Conrad Hoffman]

When you do manage to boil it, don't breath the vapors/fumes!

[HackedFridgeMagnet]

Depends on the pressure

[DaJMasta]

Yep, lead is 1750C and tin is 2600C, so if you get up there high enough, the lead will start boiling and keep things "cool" around 1750C until it's all gone.

If it's "only" 1000C, you're probably fine.  The flux or other impurities would be my concern, but it sound's like you've considered it.

[Psi]

Yeah

Thanks everyone

[Domagoj T]

Just out of curiosity, if you have a TIG torch, why would you braze with solder and not silicon bronze?
Or use silver solder, which is much stronger than electronics solder, but can be done with propane torch, without risk of melting steel, something that TIG can easily do, which when mixed with bronze leads to brittle joints.

[Zero999]

Be careful, it doesn't have to boil, to emit a toxic vapour. Any substance in its liquid phase will evaporate to some degree, it's just negligible with solder at normal soldering temperatures. The closer a liquid gets to its boiling point, the faster it will evaporate. Mercury emits enough vapour to be toxic, at room temperatures, if it's in a confined space and I think the same will be true with solder, at very high temperatures.

[Psi]

Just out of curiosity, if you have a TIG torch, why would you braze with solder and not silicon bronze?
Or use silver solder, which is much stronger than electronics solder, but can be done with propane torch, without risk of melting steel, something that TIG can easily do, which when mixed with bronze leads to brittle joints.

Mainly because i have lots of solder and was curious if it would work or not.

I do have some phosphor copper, which i think can also be used to braze. So might try that

[ConKbot]

Be careful, it doesn't have to boil, to emit a toxic vapour. Any substance in its liquid phase will evaporate to some degree, it's just negligible with solder at normal soldering temperatures. The closer a liquid gets to its boiling point, the faster it will evaporate. Mercury emits enough vapour to be toxic, at room temperatures, if it's in a confined space and I think the same will be true with solder, at very high temperatures.

https://www.powerstream.com/vapor-pressure.htm has a couple charts that would be relevant.

Mercury is about 3x10^(-3) at room temperature.  It looks like lead is the same around 670C

But i wouldn't even be able to begin to estimate what was comparable or safe, as the lead vapor will quickly chill, (into particulates in the air? Condensing on nearby surfaces? React with oxygen and make a more water soluble lead-oxide dust? ) I'd suspect the bioavailability/danger would be different than mercury entering the body in a gas phase. Either way is suspect that lead on a red-orange hot metal would present at least some danger from vapor.   

[coppercone2]

does the liquid metal eutetic form a azeotrope when it boils or no?

[Kleinstein]

I would not expect a eutectic system to also show an azeotrope.

A eutectic system is usually found if the 2 metals don't like to mix well in the solid, but do mix in the liquid.
An azeotrope is more found of the 2 components like each other very much in the liquid state so that the liquid is rather stable.
So it may happen but is not likely.

[IanB]

Yep, lead is 1750C and tin is 2600C, so if you get up there high enough, the lead will start boiling and keep things "cool" around 1750C until it's all gone.

That isn't quite how chemistry works. The boiling point of a mixture of substances is different from the boiling point of either pure substance. So for example the boiling point of an alloy of 60% tin, 40% lead is likely to be closer to the boiling point of tin than of lead.

I cannot find quantitative data on the actual numbers since apparently the boiling of such alloys is not industrially or practically useful. However, since tin and lead adjacent to each other in the same group (14) of the periodic table they are likely to form a nearly ideal mixture. As such the boiling point of solder would be approximately half way between tin and lead.

[coppercone2]

uh then how could you distill stuff? that's only true if it forms a azeotrope.

[IanB]

uh then how could you distill stuff? that's only true if it forms a azeotrope.

Actually no, it's true all the time.

There is a common misconception that when you distill things, "the lightest substance distills over first", as if first the lightest thing boils off as a pure substance, and then the next thing boils, and so forth. This is a bit of an oversimplification and it is not exactly what happens. The reality is more complicated than this simple picture implies.

What really happens is that the whole mixture boils, but the vapor coming off is richer in the lighter components than the liquid left behind. In a distillation apparatus the vapor is made travel up a column (maybe the long neck and glass tube attached to the flask in a laboratory apparatus). As the vapor travels up this column some of it condenses and falls back down while the rest of the vapor travels upwards as the temperature falls. By the time the vapor reaches the condenser it has ideally fallen to the boiling temperature of the substance you want to collect (a thermometer is used to check this). At that point what you condense should be your nearly pure product. But this only works if you carefully control the boiling rate and the condensing temperature.

On the other hand, if you simply make a mixture of water and alcohol and boil it in an open vessel (danger, do not do this indoors), the vapor that comes off will be a mixture of water and alcohol too. You will not be able to achieve any meaningful separation by this means.

[coppercone2]

i found usually even if you leave something out in a open dish you get a decent amount of purification but it depends on how close the boiling points are. its the effect of vapor pressure/ake of stuff at the surface. the coefficents are different across temperature though I think.

i think the effect of backflow purification is more related to vapor/liquid infusion/solubility then condensation, you actually don't want a temperature gradient on your fractioning column. This is why you want very high surface area in a fractioning column. Good ones are actually vacuum insulated and silvered. I think this is why a spinning band column works, because you are increasing gas pressure on the film surface, but I need to study that more. I think if the gas molecule has velocity from the spin drag then you have more diffusion of molecules into the fluid film with bigger momentum.

[IanB]

i think the effect of backflow purification is more related to vapor/liquid infusion/solubility then condensation, you actually don't want a temperature gradient on your fractioning column. This is why you want very high surface area in a fractioning column. Good ones are actually vacuum insulated and silvered. I think this is why a spinning band column works, because you are increasing gas pressure on the film surface, but I need to study that more. I think if the gas molecule has velocity from the spin drag then you have more diffusion of molecules into the fluid film with bigger momentum.

FYI, I am a chemical engineer and I know quite a lot about how distillation works. We ChemE's design and operate distillation columns for a living.

A temperature gradient is exactly the thing that makes a fractionating column work. The temperature gradient up the column is the driving force that allows the separation to be achieved. Even though the column may be insulated there is still a temperature gradient due to the varying composition of the material inside the column.

Industrial scale fractionating columns work by putting heat in at the bottom in a reboiler and taking heat out at the top through a condenser. Some of the condensate is refluxed back into the column so that there is vapor flowing up the column and liquid flowing down the column.

Putting heat in at a high temperature and taking heat out at a lower temperature means that thermodynamic work is being performed, and this work is used to separate the different molecules apart that are mixed together in the feed. When the different molecules got mixed together there was an increase in entropy, and to undo that mixing you have to put energy into the system to reverse the process.

Laboratory scale distillation apparatus is not necessarily as efficient as industrial apparatus, but it works using the same principles.

[coppercone2]

then why do hempel beads and other fillers like specially woven stainless steel braid that increase surface area increase theoretical plates without increasing length? They are used to the point where they become clog dangers (i.e. virguex column vs proper column)? It's known that a proper column filled with hempel beads, stainless steel shavings, etc, does a better job but is much harder to use then a simple low surface area column of the same length that is used unmonitored.

I am not trying to be condescending it was my understanding of it that its diffusion into a large surface area of liquid flow. I thought it would work just the same if its isothermal so long you have flow along the interior surface area of the column and vapor crashing into it? I thought the function was much different then a condenser, with the rate of condensation being important only enough to wet the walls. I was under the impression that not having a temperature gradient in the column, only down flow, results in easier control. I believe but now am unsure of it being mainly related on path length of the gas travel in regions covered by downwards moving film and that it was primarily related to absorption into the film and that the different absorption rates of the gas mixture into the film result in purification.

Do you understand it having to do with gas turbulence instead (what else does a filler in a silvered vacuum insulated column do? In that case why does it need to be wetted?

I mean this for a single stage seperator not something advanced like in a petroleum plant.

[IanB]

There are two factors at play in a fractionation column. The first factor is equilibrium between vapor and liquid, and the second factor is mass (and heat) transfer across the vapor liquid phase boundary. The simplest model of fractionation assumes that equilibrium is reached between vapor and liquid in each theoretical stage. (The reason this might be called a theoretical plate is that industrial columns commonly use actual metal plates with holes in to bring the vapor and liquid into contact.)

As with electronics you have models with varying degrees of rigor, some models making simplifying assumptions to reduce the complexity. One of the assumptions commonly made is that fractionation columns can be modeled as a series of equilibrium stages. More rigorous models relax this assumption and consider transfer rate limitations. A halfway model assumes some kind of efficiency for each stage.

Therefore if a column contains packing instead of plates then a certain height of packing will correspond to an equilibrium stage. And better packing achieves more efficient contact between vapor and liquid, which results in a shorter height of packing to reach equilibrium. In industry, packing vendors put a lot of effort into creating more efficient packing designs.

But at the end of the day, it is equilibrium that governs what kind of ultimate separation can be achieved. Improved mass and heat transfer with better packing just allows that separation to be achieved more efficiently (i.e. in a smaller column).

What it comes down to is that the limit to the theoretically achievable separation is modeled as a sequence of equilibrium stages, and each stage will have a different temperature from the ones above and below it. You get a temperature profile because the things to be separated must have different boiling points, and as you go up the column you get more of the lower boiling substances and less of the higher boiling substances.

If two substances have very similar boiling points it becomes very difficult to separate them by distillation. You get bigger and bigger columns with more and more stages.